Sciencemadness Discussion Board
Not logged in [Login - Register]
Go To Bottom

Printable Version  
 Pages:  1    3    5  ..  21
Author: Subject: Hydrazine
Theoretic
International Hazard
*****




Posts: 756
Registered: 17-6-2003
Location: London, the Land of Sun, Summer and Snow
Member Is Offline

Mood: eating the souls of dust mites

[*] posted on 9-11-2004 at 15:24


Have a look at E&W (if you don't know about it yet then google explosives & weapons), they have it in the High explosives section, the topic is called "Urea Nitrate and Nitrourea...again".



View user's profile View All Posts By User
Mongo Blongo
Unregistered




Posts: N/A
Registered: N/A
Member Is Offline


[*] posted on 10-11-2004 at 11:58


Yea I have been there for a few years :). I read that whole thread again and still find no mention of urea DInitrate. Just urea nitrate, nitrourea and dinitrourea.
My goal IS dinitrourea as you can read in the "KETO-RDX and DIKETO-HMX" thread on the E&W forum where I have posted about a few experements.
So far I can only get to nitrourea and then it goes wrong for some reason. I am just looking for another way to achieve the dinitrourea synth.
Theoretic
International Hazard
*****




Posts: 756
Registered: 17-6-2003
Location: London, the Land of Sun, Summer and Snow
Member Is Offline

Mood: eating the souls of dust mites

[*] posted on 10-11-2004 at 13:16


I think urea dinitrate can be prepared in much the same way as urea nitrate, you just use twice as much nitric acid.
It's quite a straightforward procedure, essentially a formation of diuronium nitrate CO(NH3+)2(NO3)2




View user's profile View All Posts By User
PainKilla
National Hazard
****




Posts: 306
Registered: 29-4-2004
Member Is Offline


[*] posted on 12-11-2004 at 05:22


I will be attempting to perform the hydrazine synth using the NaOCl, urea and NaOH method. I am told that regular 6.25 is great for this because the reaction proceeds and is not too violent. However, if this does not work, would Ca(OCl)2 work? I can't figure out the equation for it. I haven't taken chemistry yet, all i know is from reading so pardon my dumbass :). Also, adding dilute h2so4 would form the sulphate without hazardous explosion hazards, yes? I will report fairly soon :p. Thanks.
View user's profile View All Posts By User
Theoretic
International Hazard
*****




Posts: 756
Registered: 17-6-2003
Location: London, the Land of Sun, Summer and Snow
Member Is Offline

Mood: eating the souls of dust mites

[*] posted on 12-11-2004 at 07:46


A useful link



View user's profile View All Posts By User
BromicAcid
International Hazard
*****




Posts: 2830
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Anxious

[*] posted on 12-11-2004 at 10:07


Ca(OCl)2 is somewhat less soluble then NaOCl and I have never seen a preparation use Ca(OCl)2, it might be advantageous because the slow rate of reaction due to slow solvation, but the alkaline environment might just pacify the top layer. I've always wanted to try with Ca(OCl)2 because it is more readily available to me, however safety was not my concern, I planed to distill the hydrazine azeotrope directly from the reaction mixture which results in a higher yield. If you do experiment with Ca(OCl)2 be sure to try many different reaction contidtions and concentrations and addition methods and keep close track of them, you could conceivably start a new trend in hydrazine production.

And yes, addition of sulfuric acid will precipiate out your hydrazine sulfate which is of somewhat low solubiliy. If you did it with calcium hypochlorite though you would also precipitate out calcium sulfate and contaminate your product, but you could always recrystalize from warm or hot water.




Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
SAM4CH
Hazard to Others
***




Posts: 162
Registered: 16-7-2004
Location: TA
Member Is Offline

Mood: PERFECT

[*] posted on 10-12-2004 at 14:10
Hydrazine KClO3


Can I get hydrazine hydrate from KClO3 instead of NaOCl solution? Please more details!
View user's profile View All Posts By User This user has MSN Messenger
MadHatter
International Hazard
*****




Posts: 1034
Registered: 9-7-2004
Location: Mid-Atlantic
Member Is Offline

Mood: Patience growing thin !

[*] posted on 11-12-2004 at 00:31
KClO3 ?


I don't know what would happen by mixing urea and a chlorate. I would NEVER mix a
chlorate with ANY compound of AMMONIA ! This may produce the very dangerous and
unstable NH4ClO3.




Power comes from the barrel of a gun !
View user's profile View All Posts By User
october-sky
Harmless
*




Posts: 1
Registered: 11-12-2004
Member Is Offline


[*] posted on 11-12-2004 at 05:47
the distillation


What about the distillation, i have all the compounds (without the nitrogen) but i dont know how to distill the hydrazine...
i only know how to make a simple distillation...
View user's profile View All Posts By User
chemoleo
Biochemicus Energeticus
*******




Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline

Mood: crystalline

[*] posted on 11-12-2004 at 12:50


No, you can't use KClO3, as much as you can't use KClO4, or KMnO4, or whatever. It's the -OCl you are after, because it reacts with the NH3 in such a manner that chloramine H2NCl is transiently produced.

As to distillation - if you read the thread carefully - it is commonly recommended to PRECIPITATE the hydrazine with H2SO4. No distillation involved. I wouldn't recommend it anyhow as distillation sometimes leads to explosions.

Comon guys, read the threads before you post obvious stuff!

[Edited on 11-12-2004 by chemoleo]




Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
View user's profile View All Posts By User
SAM4CH
Hazard to Others
***




Posts: 162
Registered: 16-7-2004
Location: TA
Member Is Offline

Mood: PERFECT

[*] posted on 15-12-2004 at 06:10
NaOCl from NaCl!


Can I get pure NaOCl with electrolysis of NaCl as a method like preparing NaClO3?!

Please I need more detail for the cell current, running time, and others to improve my Chlorate cell to make pure hypochlorite.




Sam
View user's profile View All Posts By User This user has MSN Messenger
BromicAcid
International Hazard
*****




Posts: 2830
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Anxious

[*] posted on 15-12-2004 at 10:05


I think the key difference between a chlorate cell and a hypochlorite cell would be the cell temperature. Keep it low and hypochlorite would be favored. You might want to keep the current density a little lower too to prevent further oxidation of the hypochlorite.

BTW, I've tried many times to prepare hypochlorite insitu for reactions with electrolysis with little sucess, being that hydrazine is somewhat sensitive to impurites, making your own hypochlorite might be benifical, however you will have to use electrodes that will be both inert to the oxidation process of the electrolysis and that if they leave contaminates in the solution will not affect hydrazine production.

[Edited on 12/15/2004 by BromicAcid]




Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
Marvin
International Hazard
*****




Posts: 991
Registered: 13-10-2002
Member Is Offline


[*] posted on 15-12-2004 at 13:42


Might I suggest setting up a chlorine cell, or even just a chemical chlorine generator and leading that into sodium hydroxide. There is little point in having the hypochlorite generated in the electrochemical cell itself. The chloride formed as well should not affect anything.
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6071
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 15-12-2004 at 19:45


Another option for you if you can't obtain 10% pool chlorinator sodium hypochlorite ,
but do have access to ordinary bleach concentration 5% or 6.25% sodium hypochlorite , and also have available calcium hypochlorite and washing soda , is to increase the concentration of the bleach you can get . The strategy would be to dissolve in the bleach sodium carbonate sufficient for producing the further amount of sodium hypochlorite needed to bring up the concentration to the desired level . Then to the stirred solution add calcium hypochlorite sufficient to react with the sodium carbonate , and filter out the calcium carbonate byproduct to obtain your more
concentrated sodium hypochlorite . A slight excess of theory of sodium carbonate should be used to insure that all the calcium ion is precipitated as carbonate . Or a slight added amount of baking soda could be used to finish the reaction and cleanup any remaining calcium which may persist in solution .
Washing soda as obtained from the grocery store is a partial hydrate so you should perform a weight loss on heating and drying test to determine the actual content of Na2CO3 . For example I baked 500 grams of washing soda for a couple of days and it lost 83 grams of water .
You could test twenty grams of your calcium hypochlorite separately to see just what amount of your washing soda is required to precipitate all the calcium , until futher additions of the sodium carbonate solution cause no clouding when mixing , to arrive at an "equivalence" ratio for the two reactants . You can then use that figure and do the math to know how much of each will be reacted in solution with your bleach to increase its concentration to whatever you desire , but 10 or maybe 12% at most is all you really need for the hydrazine from urea and sodium hypochlorite process . I have not actually tried this proposed method , but it would seem to be more direct than producing gaseous chlorine and reacting it with sodium hydroxide . One thing you must do is to keep the temperature low as possible and not permit any warming of the reaction mixture to occur for any extended time of even a few minutes or the hypochlorite will be destroyed . Very moderate and preferably cool temperatures are favored , if the reaction will proceed in the cold , even better .
View user's profile View All Posts By User
tokat
Hazard to Self
**




Posts: 64
Registered: 1-6-2004
Location: 6feet south
Member Is Offline


[*] posted on 18-12-2004 at 23:13


and any execcess of water the thing will ignite, Use small amounts of compounds.
View user's profile View All Posts By User
garage chemist
chemical wizard
*****




Posts: 1805
Registered: 16-8-2004
Location: Germany
Member Is Offline


[*] posted on 21-4-2005 at 13:15
My hydrazine attempt using Mr Anonymous' method


About two years ago I made hydrazine sulfate with Mr. Anonymus' method. From 475ml of 10% NaOCl I got 15g HS. It was a terrible mess, the amount of foam was about ten times the initial volume of the solution and the reaction mixture poured out of the 2 L Erlenmeyer over my bare hands on the table and on the floor (I was really careless back then). I hope I didn't suffer any nerve damage from the hydrazine. Had some fun when I searched on the internet for the dangers of hydrazine (of course after getting it on my hands).

But once I had the HS, the rest of the synthesis was fun and a piece of cake.
To produce a maximum concentration hydrazine hydrate, I mixed the dry HS with an excess of NaOH and ground it in a mortar and pestle and distilled it. I got several ml of slightly fuming liquid.
The glass round bottom distilling flask was heavily attacked, though. This was not ideal.

I didn't like the freebasing method into methanol, and I didn't have any methanol so I chose to distill it.

I reacted it with isopropyl nitrite in ethanolic NaOH, it became quite warm and the IPN boiled away! Be sure to use an excess of IPN and cool it in an ice bath once the reaction has started.
(IPN was extremely easy to produce by slowly dripping HCl into a stirred solution of IPA and NaNO2 in water at 0°C, the IPN floats to the top and is separated and washed with water and bicarb soln. I used molar amounts, the IPN yield was high.)

The final yield was 3g of white fluffy stuff that deflagrated when heated and left small metallic globules which burned with a yellow flame.


E. b. C.: title

[Edited on 1-5-2005 by chemoleo]
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6071
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 21-4-2005 at 16:24


Quote:
Originally posted by garage chemist
About two years ago I made hydrazine sulfate with Mr. Anonymus' method. From 475ml of 10% NaOCl I got 15g HS. It was a terrible mess, the amount of foam was about ten times the initial volume of the solution


You had to be doing something differently from the way the writeup described , because a volume increase of triple is
about average , sometimes a bit more but
quadruple would be the maximum and very unusual .....never ten times , unless
a spill of hydrazine just has a way of looking like a lot bigger mess than it is ;)

Quote:
and the reaction mixture poured out of the 2 L Erlenmeyer over my bare hands on the table and on the floor (I was really careless back then). I hope I didn't suffer any nerve damage from the hydrazine. Had some fun when I searched on the internet for the dangers of hydrazine (of course after getting it on my hands).
No biggie for the dilute solution . HS is even taken medicinally as an experimental cancer drug . Hydrazine is destroyed so rapidly
by the air , you could come back to the area in a few hours , and there wouldn't be any of it left . No decontamination required , oxygen took care of the problem .
Quote:

But once I had the HS, the rest of the synthesis was fun and a piece of cake.
To produce a maximum concentration hydrazine hydrate, I mixed the dry HS with an excess of NaOH and ground it in a mortar and pestle and distilled it. I got several ml of slightly fuming liquid.
The glass round bottom distilling flask was heavily attacked, though. This was not ideal.


There is no need to distill . You have the freebase , so just extract it with alcohol
and then nitrosate it .
Quote:

I didn't like the freebasing method into methanol, and I didn't have any methanol so I chose to distill it.


Microtek has reported at E&W that the hydrazine can be freebased into anhydrous isopropyl alcohol using a special technique and proportions .

Quote:

I reacted it with isopropyl nitrite in ethanolic NaOH, it became quite warm and the IPN boiled away! Be sure to use an excess of IPN and cool it in an ice bath once the reaction has started.


Everything needs to be cold at the start and through to nearly the end . When your isopropyl nitrite contacts the ethyl alcohol , transesterfication produced some ethyl nitrite , which is more volatile
and escapes more easily from a mixture that is not cold .

Quote:

(IPN was extremely easy to produce by slowly dripping HCl into a stirred solution of IPA and NaNO2 in water at 0°C, the IPN floats to the top and is separated and washed with water and bicarb soln. I used molar amounts, the IPN yield was high.)


A slight excess of theory of NaNO2 to HCl should be used and a slight excess even further of isopropanol . This will result in a more stable product and even higher yield .

In my experience with making IN different ways , it is preferable to premix your ice cold alcohol and ice cold HCl , and to chill a concentrated solution of NaNO2 separately . Put the additional water which will be needed in the completed reaction mixture to insure the solution of the NaCl byproduct , as ice cubes in the empty reaction flask , and chill down everything in the freezer . When you remove the flask of ice cubes and pour over the cubes the very cold brine of NaNO2 , the mixture self cools from the salting effect , as the HCl and alcohol is
run in rapidly through a tube extending to the bottom of the stirred mixture . You can make 200 grams of IN in 15 minutes by this method , and it separates pure in a floating layer with the nearly melted ice ,
which rinses it as it melts , right where it is floating . If you use some solid ice cubes in the reaction mixture , they float in a layer with the precipitated IN and rinse the IN in situ . All you need to do is separate the product with the nearly melted cubes by decantation into a funnel , drain off the lower aqueous layer , and dispense the IN into a cold bottle having a teflon gasket , or a glass stoppered bottle . IN attacks anything else . The IN can be stored in the freezer .

It is very possible that the IN does not even have to be made separately if the hydrazine has been freebased into anhydrous isopropanol . The isopropanol
solution of hydrazine hydrate is basified with NaOH in equimolar amount to the HS which was freebased , and then the basified solution is treated with N2O3 ,
forming the IN in situ as a transient species , or reacting directly with the hydrazine , in either case causing NaN3
to precipitate . Microtek reported success
producing IN by bubbling through cold isopropanol N2O3 evolving from a warmed mixture of ~60% HNO3 and starch , via a smooth and steady decomposition of the HNO3 . Producing and isolating the IN separately is possibly
not necessary , if you follow the logic ,
but simply bubble the N2O3 directly into
the basified hydrazine extract in isopropanol . No one has tested this idea
so far as I know .
Quote:

The final yield was 3g of white fluffy stuff that deflagrated when heated and left small metallic globules which burned with a yellow flame.


You got some NaN3 , but wouldn't you like to have more grams for your effort ?

More thoughts about the HS procedure .....

The formation of hydrazine from urea is
definitely not without an indication that
some small reaction is occurring ;)
It is almost unbelievable until you see
it yourself isn't it , just how much foam
can be afoot quickly as if it were a stampeding hydrazine " moose " :D

The first time I made hydrazine by the urea - pool chlorinator method , I had an overflowing mess too , so I kept working at refining the method until I had it down to an art . It very likely will make a mess if you start the reaction without allowing
it plenty of " room to grow " :D , and even
CYA with some overflow and return path like a really large funnel fitted snugly
into the neck of the flask . But if you do follow the directions given at great length
in the " improved " synthesis writeup ,
good results and yields will be predictable . Once you see it does work
in the way described , it will be a breeze to make up HS , even in large batches .

I have kilos of hydrazine sulfate as the product of many experiments studying the reaction , and it really is a simple synthesis after learning how the reaction behaves and how essential it is to allow it plenty of space .

When I make the HS , I use a half gallon
of hypochlorite in a batch run in a 4 liter
Erlenmeyer with a like capacity overflow funnel . I have a 12 liter flat bottom Florence so I could probably run a batch
using a full gallon of hypochlorite at one time and keep everything tidy by fitting
a five gallon plastic bucket with a rubber bushing and using it atop the flask as an overflow and return , in case the foam became excessive . Not exactly microscale , but saves work over several smaller batches . However unless you have some insane need for huge quantities of HS , a 4 liter erlenmeyer batch size is plenty for most folks .
Even with your 2 liter erlenmeyer you can make whole lot more in a controlled fashion than 15 grams . You should have gotten at least 55 grams . Keep the batches small until you know the reaction well , and then you can maximize the yield later . The reaction is sensitive to small variables which you will see if you do the synthesis a few times .

[Edited on 22-4-2005 by Rosco Bodine]
View user's profile View All Posts By User
garage chemist
chemical wizard
*****




Posts: 1805
Registered: 16-8-2004
Location: Germany
Member Is Offline


[*] posted on 23-4-2005 at 06:26


Thanks for the interesting info!

I just stuck 475ml of NaOCl in the freezer and dissolved 0,7g gelatin and 45,5g urea in 50ml water. Tomorrow I will try the HS synthesis another time.

I will dissolve the 64g NaOH in 60ml water and add it to the ice-cold NaOCl in liquid form to reduce heat evolution. I hope this will allow me to add all the NaOH at once.

A question: how did you stir the mixture? I only have a 5cm magnetic stirring rod and the 475ml NaOCl only stands about 3-4cm high in the 2L Erlenmeyer. So only the inner portion of the liquid is stirred, and the outer part moves rather slow. Should I still add the urea/gelatin solution all at once into the "vortex"?

EDIT: This was written by microtek in the E&W (I'm not registered there, got acess to the forum by using the google cache) :

"For sodium azide production I use a method which gives hydrazine in alcohol ( from hydrazine sulfate ) with little or no water:

- 1 mol dry HS is placed in a flask along with a suitable amount of anhydrous isopropanol.
- 1 mol of NaOH pellets are added and the contents are triturated with a glass rod until they begin to react, forming a slurry of hydrazine hydrate and NaHSO4. This doesn't mix with the iPrOH, but forms a sticky goo on the glass.
- Another 1 mol NaOH is added which converts the NaHSO4 to Na2SO4 ( and forms a mol of water ) which separates cleanly as a white powder.
I would think that the Na2SO4 is a good enough dessicant to dry out the solution which can then be decanted.
- Another extraction or two with dry iPrOH recovers most of the hydrazine.

This alcoholic solution of hydrazine works well for producing sodium azide with isopropyl nitrite."


Is this the method you're referring to, Rosco?
How much isopropanol should be added?



[Edited on 23-4-2005 by garage chemist]
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6071
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 23-4-2005 at 07:49
For best results follow Mr. A's method *exactly*


Because that method has been carefully optimized already , and any thing you do to change things even in a small way will
cause a disproportionate negative effect .
Do the procedure the way it was described *first* to confirm it works , and then change things to prove the * small * changes adversely affect the reaction in much * larger * ways you wouldn't have expected :D Been there , done that .

Quote:
Originally posted by garage chemist
Thanks for the interesting info!

I just stuck 475ml of NaOCl in the freezer and dissolved 0,7g gelatin and 45,5g urea in 50ml water. Tomorrow I will try the HS synthesis another time.

I will dissolve the 64g NaOH in 60ml water and add it to the ice-cold NaOCl in liquid form to reduce heat evolution. I hope this will allow me to add all the NaOH at once.


Hmmmm , that is counterintuitive because
that will *increase * the exotherm by heat of dilution at the very moment the reaction is initiating , and you will likely produce a geyser , instead of a slowly rising foam . Again , do it first the way Mr. A has described . The thermodynamics are already worked out for controlling the reaction , and they are as described .

Quote:

A question: how did you stir the mixture? I only have a 5cm magnetic stirring rod and the 475ml NaOCl only stands about 3-4cm high in the 2L Erlenmeyer. So only the inner portion of the liquid is stirred, and the outer part moves rather slow. Should I still add the urea/gelatin solution all at once into the "vortex"?


You quickly pour in a steady stream the urea and gelatine into the well stirred cold basified hypochlorite . Just pour it in
quickly , " in a lump " as the expression
goes . You should have one to two minutes before the foaming begins ,
so you have plenty of time to mix the two liquids if you pour the urea-gelatine solution in without any delay , the idea being to get it all in and mixed before the
foaming will complicate adding anything .

You should really have a 3" stirbar , even in a two liter flask , the octagon sort 3" X 1/2" should do okay . And yes , at first you have to reduce the stirring speed to keep the shallow pool from splashing and just pull as good a " swirling " shallow vortex as can be managed . The speed can be increased later as the foam begins to rise so that the stirbar is actually churning through and tearing apart the foam and helping to break apart the bubbles so that it returns to a liquid state and very slowly settles out again as a lower layer , over the course of the reaction , which may take a half hour or more . Everything about what happens has been described in Mr. A's very detailed description . Trust the information as a lot of work and many experiments were done to pin down all those important details .

The sequence of preparation of the reagents is important , the temperatures
and how the prepared reagents are added together is also important .
The reaction * is * sensitive to small variables and they have all been covered
in the described procedure , so don't deviate one iota in the belief that it probably won't make any difference , because just the opposite is probably true instead :D

And please , for anybody who makes arbitrary changes in one of Mr. A's or
Rosco's described experiments and then gets a different result , understand that what detail was thought not to be consequential , was indeed consequential . For every process where it is described what works , there are unwritten volumes about variations on the method which don't work , and when something is changed about a procedure ,
it usually does matter , even if the reason is not obvious why that change should have any bearing on the outcome . The troubleshooting of the variables has usually already been done for those procedures where exacting methods have been detailed . So roll that ready made wheel first and see how it goes , before
reinventing it in any detail and then saying it isn't round :D
View user's profile View All Posts By User
garage chemist
chemical wizard
*****




Posts: 1805
Registered: 16-8-2004
Location: Germany
Member Is Offline


[*] posted on 23-4-2005 at 07:55


Hmm, I understand that the method is optimized, but I can't imagine that the way the NaOH is dissolved in the NaOCl is of such importance. The only important thing is to keep it cool, right? Also, there is no gas evolution in this step. Urea and gelatin are added much later!
Perhaps this is a misunderstanding?
View user's profile View All Posts By User
The_Davster
A pnictogen
*******




Posts: 2856
Registered: 18-11-2003
Member Is Offline


[*] posted on 23-4-2005 at 08:40


I must say, Rosco your HS synthesis does work very well. I attempted it for the first time last night and it went almost exactly as desribed. I did it on 1/32 the scale so yields will be lower from mechanical losses, but the synthesis went smoothly. Even the foam heights you described were the same, which while that will not surprise you, it did surprise me.



View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6071
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 23-4-2005 at 08:53


Quote:
Originally posted by garage chemist
Hmm, I understand that the method is optimized,


Correct . Don't change things in an optimized method .

Quote:

but I can't imagine that the way the NaOH is dissolved in the NaOCl is of such importance.


Because the heat of dilution is huge and
it will cause too much heat to add
it all at once , both for the stability of the hypochlorite and for the controlability of
the reaction producing hydrazine . You are
also adding water to the system by predissolving the NaOH . This alone will
diminish the yield and is compounded by
the other problems which will be caused .

Quote:

The only important thing is to keep it cool, right? Also, there is no gas evolution in this step. Urea and gelatin are added much later!
Perhaps this is a misunderstanding?


You are trying to apply linear two dimensional thinking to a much more complex scenario than lends itself to such analysis . You can trust me on that or you
can prove it for yourself with failed syntheses by testing your theories in
the flask . Lets not debate the theory .
Better to talk about the comparisons of
experimental results later , and what may be concluded from what actually occurs .
Anyone is welcome to make whatever improvements on the methods are valid ,
and describe their improved yields and
all of the details about how this was achieved . But that is for later , after the
proof is established by the results of their
experiments , not by estimates in advance
of what results are unknowns until such
experiments are completed .

rogue chemist :

Thanks for the confirmation .

I know my own work pretty well on procedures and methods that are
either completely my invention or
are variations and /or improvements
upon already known methods . And
I'm never afraid to say " I don't know "
but this isn't one of those times :D

[Edited on 23-4-2005 by Rosco Bodine]
View user's profile View All Posts By User
garage chemist
chemical wizard
*****




Posts: 1805
Registered: 16-8-2004
Location: Germany
Member Is Offline


[*] posted on 23-4-2005 at 09:02


I just find it easier to add a NaOH solution to the NaOCl (maybe even drop- wise) than to add solid NaOH, which dissolves very slowly and the solution needs to be chilled between the additions.
But if you say that it is so important to add the NaOH in solid form, I will do so.

In my synthesis (2 years ago), the foam was produced INSTANTLY when I added the urea/gelatin. Maybe the NaOCl was too warm? The ice on the outside of the erlenmeyer had just melted.
Does adding the urea/gelatin to the NaOCl at sub- zero temperatures greatly diminish the yield?

I will attach a 3-inch glass rod to my small stirring rod to make a big one. I hope this helps.
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6071
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 23-4-2005 at 09:58


Quote:
Originally posted by garage chemist
I just find it easier to add a NaOH solution to the NaOCl (maybe even drop- wise) than to add solid NaOH, which dissolves very slowly and the solution needs to be chilled between the additions.
But if you say that it is so important to add the NaOH in solid form, I will do so.

Yes it is easier , and I have done it that way too , once . It decreased the yield ,
and the hypochlorite still required being
prechilled , because the heat of dilution is still huge , even if the NaOH is initially dissolved in a minimal amount of water .
The NaOH dissolves easily in the well stirred very cold hypochlorite . So there is
no reason not to do it the way which gives
the best result .
Quote:

In my synthesis (2 years ago), the foam was produced INSTANTLY when I added the urea/gelatin. Maybe the NaOCl was too warm?


Too warm or you didn't use distilled water
for the urea-gelatine , or your stirring was inadequate and/or the addition of the urea-gelatine was done too gradually .
Usually there is at least 30 seconds before
the foaming begins to rise . The mixture
clouds almost immediately and lightens in color from a gazillion microscopic bubbles ,
self-heating accelerates and then a surge
of rising foam steadily rises .
Quote:

The ice on the outside of the erlenmeyer had just melted.
Does adding the urea/gelatin to the NaOCl at sub- zero temperatures greatly diminish the yield?


It slows the reaction to initiate at below about 3 to 5 C , slows the induction and extends the total time , decreases the yield slightly , and can actually increase
the total volume of foam produced . The
thermodynamic curve the reaction follows
is something of a tradeoff between reaction rate , volume of foaming , and yield , which has a sweet spot a few minutes after the reaction is begun where
the increasing temperature actually causes the foaming to dissipate more quickly . When you start the reaction too cold , the gentle exotherm of the self-reaction doesn't allow the mixture to heat up on its own to reach that desirable temperature , where the foam is destabilized and begins to disintegrate on its own . This extends the overall time for the reaction and the volume which the foam expands is increased , above what total volume would be if the initial temperature was higher .
But if the reaction is started too warm , then the foam height increases too rapidly and again the total volume is increased .
So there is a " window " temperature range for the reaction start that is ideal for a particular batch size , and stirring efficiency , and it will differ for a different batch size because of the different radiational heat loss and latent heat characteristics for a different geometry
for that different sized reaction mass .

Quote:

I will attach a 3-inch glass rod to my small stirring rod to make a big one. I hope this helps.


You could probably put your smaller stirbar inside of a hollow poly tube like
an old marker pen or similar into which it would fit snugly , and provide a bit of extra diameter and length . Size does matter :D although you will have to watch the speed to keep it from uncoupling in
the mixture . There's nothing in this reaction which should terribly attack the
poly , although I haven't tried this to make certain . Just make sure you keep the stirring going throughout the reaction . You will see the spiraling bands
in the foam indicating that the entire mass of foam is actually moving , especially just before it begins to disintegrate of its own accord as you are
ramping up the heating .

Something you really should do is provide some expansion room and return path for any potential overflow . If you dont have
a large funnel handy , then cut the bottom
out of a 3 liter PET soda bottle and invert it and secure the open neck of the soda bottle in the open neck of the flask with
a sleeve bushing cut from a large diameter
hose , or perhaps simply duct tape the necks of the two vessels together . Whatever overflow occurs will rise up into
the soda pop bottle and then flow right back down into the flask as the foam disintegrates with passing time . Sit a small soup bowl or cereal bowl or saucer
in the opening where you have removed the bottom of the bottle , after you pour
the urea-gelatine down through the opening and into the flask . Just dump and cover . You should be able to scale up at least 50% from the 475 ml , and perhaps 75% more without any overflow .

Whatever the scale you use , keep to exactly the described relative proportions
on every ingredient . The amount of gelatine will have significant bearing on
the reaction so weigh it carefully and make sure your glassware is very clean
and definitely use only distilled water .
Metal ions poison the reaction .

[Edited on 23-4-2005 by Rosco Bodine]
View user's profile View All Posts By User
The_Davster
A pnictogen
*******




Posts: 2856
Registered: 18-11-2003
Member Is Offline


[*] posted on 23-4-2005 at 21:25


Well shit, I may have hydrazine poisoning. I have had a headace and had some nausea today, symptoms of hydrazine poisoning.:( As well I have felt weird today, not a way I have felt before. I wore a respirator the entire synthesis, except during filtration.

It could just be that I'm a bit of a hypochondriac, and this is just a placebo type effect. But I am still worried.

:(




View user's profile View All Posts By User
 Pages:  1    3    5  ..  21

  Go To Top